Patent GB-580740-A (GB)
Title: Improvements in or relating to the preservation of rubber or rubber-like materials
IPC: C08K5/18
Filed: 1943-07-13
Abstract: Rubber or rubber-like materials including caoutchouc balata, gutta-percha, latex, reclaimed rubber, artificial rubber isomers, polychloroprene, copolymers of butadiene with acrylonitrile, styrene, methylacrylate, methyl methacrylate and isobutylene, are protected from oxidation by incorporating therewith a product obtained by the nuclear alkylation of a diarylamine with an alkylating-agent containing at least five carbon atoms in amounts ranging from 0.1 per cent to 5 per cent or more of the composition.  Specified diarylamines are diphenylamine, phenyl - a  - naphthylamine, phenyl-b -naphthylamine, the ditolylamines, the phenyltolylamines, the dinaphthylamines, anilinotetraphenylmethane, phenyl-p-xenylamine, dixenylamine, dianilinodiphenylmethane, p - hydroxydiphenylamine, p - aminodi - phenylamine, N,N1 - diphenyl - p - phenylene - diamine, anilino - acridine, 6 - anilino - quinoline, p - chlorodiphenylamine, phenylindanylamine, indanyl-a -naphthylamine, indanyl - b  - naphthylamine, diindanylamine anilino - biphenylene oxide, and p-isopropoxydiphenylamine.  Preferred alkylation catalysts are those of the Friedel-Crafts acid condensation type, e.g. hydrogen chloride, sulphuric acid, aluminium chloride, boron trifluoride, sodium bisulphate, zinc chloride, stannic chloride, ammonium bromide, iodine and phosphoric acid; while the alkylating-agents which are applicable comprise the alkenes, alkanols, alkyl halides or dialkyl ethers. Although a single purified compound, e.g isoamyl alcohol or n-hexyl chloride may be used as the alkylating-agent, a mixture of isomers or homologues is, in practice, found to be more readily available and equally effective.  The composite product formed by the alkylation reaction is used as the antioxidant, i.e. the mixture of isomeric and homologous compounds from which the catalyst and unreacted starting-materials have been removed.  It is desirable also to p remove the dark-coloured high-boiling by-products present in small amounts.  Representative examples of suitable alkylating-agents are given, ranging from pentenes to 3-nonene, and from pentanols to decanols, including the methyl or ethyl substituted derivatives. Alkylation may be effected either at atmospheric or at elevated pressures and at temperatures ranging from 50 DEG  to 300 DEG  C., depending upon the particular alkylating-agent and catalyst used.  In examples: (1) a mixture of diphenylamine, 2-pentene and zinc chloride is heated in an autoclave to about 300 DEG  C., the catalyst is removed by washing the product, and distillation yields unreacted diphenylamine and a yellowish oil of boiling-range 125-175 DEG  C. at 1 mm. pressure, which probably consists chiefly of monoamyldiphenylamine, but contains also a small amount of di- and polyamyldiarylamines; (2) a mixture of diphenylamine, aluminium chloride and mixed heptenes obtained by the cracking of petroleum is heated at 150 DEG  C. in an autoclave and, after washing, the product yielded, on distillation at 1 mm. pressure, a low-boiling fraction, unreacted diphenylamine and a dark brown oil of approximate boiling-range 155-235 DEG  C., of which over 80 per cent comprised monoheptyl diphenylamines, the remainder being more highly substituted; (3) the yellowish oil obtained as in (1) at a temperature of 250 DEG  C. is as an antioxidant in a synthetic rubber composition; (4) a mixture of diphenylamine, aluminium chloride and mixed octenes from the cracking of petroleum is heated at atmospheric pressure at 150 DEG  C., the product being washed with brine and a solution of alkali prior to fractional distillation at 1 mm., to yield a low-boiling fraction, unchanged diphenylamine and a yellowish oil of boiling-range 165 DEG  to 230 DEG  C., consisting chiefly of mono-octyl diphenylamines; (5) a similar mixture to the one in (4) substituting zinc chloride for aluminium chloride, on distillation at 1 mm. leads to a product of boiling-range 180 DEG  to 240 DEG  C.; the fraction boiling at 180-190 DEG  C., stated to consist chiefly of the mono-octyl diphenylamines, is used as a non-staining antioxidant; (6) diphenylamine diisopropyl carbinol and zinc chloride are heated under reflux at atmospheric pressure at about 200 DEG  C. and the product, after washing, is distilled, yielding a low-boiling fraction, unchanged diphenylamine, and a dark-coloured oil of boiling-range 155 DEG  to 235 DEG  C., more than 80 per cent of which consisted of the mono-alkylated diphenylamines. Specifications 410,274, [Group V], 483,605, 561,999 and 563,479 are referred to. The Specification as open to inspection under Sect. 91 comprises also the preservation of oxidisable organic materials generally. This subject-matter does not appear in the Specification as accepted.ALSO:Rubber, or rubber-like materials, including caoutchouc, balata, guttapercha, latex, reclaimed rubber, artificial rubber isomers, polychloroprene, copolymers of butadiene with acrylonitrile, styrene, methylacrylate, methyl methacrylate and isobutylene are preserved by incorporating therewith a non-staining antioxidant obtained by the nuclear alkylation of a diarylamine with an alkylating agent containing at least five carbon atoms in amounts varying from about 0.1 to 5.0 per cent. or more of the rubber composition.  Their effect is not destroyed by the presence of the usual pigments, fillers, dyes, softeners or accelerators in the rubber composition and incorporation is effected for example on a roll mill, in an internal mixer, by dispersion in the rubber latex or addition as a solution.  Specified uses to which rubber compositions containing the antioxidants are put are the manufacture of hose, belting, rubber threads, rubberized fabrics, footwear, moulded goods, tyres and inner tubes or latex-dipped goods.  The antioxidant used is preferably the composite product formed on alkylation, comprising the mixture of isomeric and homologous compounds from which the acidic condensation catalyst and unreacted starting-materials have been removed.  In examples: (1) the oil of boiling range 125 DEG  to 175 DEG  C. at 1mm. pressure, obtained by interacting diphenylamine, 2-pentene and zinc chloride at about 300 DEG  C. and believed to consist chiefly of monoamyl diphenylamine but containing a small amount of di-and polyamyl diarylamines, is used as the antioxidant in a composition comprising rubber, zinc oxide, magnesium carbonate, titanium dioxide, sulphur, softener, stearic acid and a mixture of mercaptobenzothiazole, dibenzothiazyl disulphide and tetramethyl thiuram disulphide; (2) the oil of boiling range approximately 155 DEG  to 235 DEG C. (at 1mm.) obtained by interacting diphenylamine, mixed heptenes and aluminium chloride at 150 DEG  C. and consisting chiefly of monoheptyl diphenylamines, is used as the antioxidant in a composition comprising rubber, zinc oxide, titanium dioxide, ultramarine blue, sulphur, and a reaction product of heptaldehyde and aniline; (3) the product of (1) is incorporated in a composition comprising a copolymer of butadiene and acrylonitrile, zinc oxide, titanium dioxide, dibutyl phthalate coumarone resin sulphur and 2-mercapto-4:5-dimethyl thiazole; (4) and (5) an oil boiling at 165 DEG C. to 178 DEG C. (1mm.) consisting chiefly of mono-octyl diphenylamines is used as the antioxidant in the composition of (3) and (4) respectively; (6) the oil of boiling-range 155 DEG  to 235 DEG  C. obtained by interacting diphenylamine, diisopropyl carbinol and zinc chloride at about 200 DEG  C. is used as the antioxidant in the composition of (2) containing wax.  Specifications 410,274, 483,605, 561,999 and 563,479 are referred to.  The Specification as open to inspection under Sect. 91 comprises also the preservation of oxidisable organic materials generally. This subject-matter does not appear in the Specification as accepted.